390 



SCIENCE 



[N. S. Vol. XL VII. No. 1216 



genous substances. Sucli a mixtvire should be 

 capable of some separation by ordinary cbem- 

 ical means. Any method of rigorous purifi- 

 cation, such as that employed in the purifica- 

 tion of lipoids, would certainly effect some 

 change in the composition of this mixture. 



Without criticizing the arguments of Bar- 

 bieri, some of which (e. g., the statement that 

 glycerolphosphoric acid may be formed during 

 the process of hydrolysis, from the glycerol of 

 the fat and dilute phosphoric acid) certainly 

 are open to criticism, we offer the following 

 argument for the existence of lecithin. 



The work of earlier workers seems to be 

 suf&cient to show that lecithin is a chemical 

 substance, even though the analyses of the 

 products from various sources (brains, heart, 

 liver, egg) did not agree very well. But if 

 any doubt existed as regards the existence of 

 lecithin, it would seem that the recent work 

 of Levene and West^ proves that such an idea 

 is not tenable. Wot only has lecithin, as such, 

 been isolated from the above-mentioned 

 sources, but derivatives have been prepared and 

 subjected to rigorous purification, always with 

 the same result. The following facts may be 

 mentioned. 



Lecithin, from various sources, such as the 

 primary alcoholic extract, the primary ethereal 

 extract, the secondary alcoholic extract, or the 

 fraction dissolved in egg oil, has been precipi- 

 tated as the cadmium chloride salt, giving a 

 product of very similar composition. This 

 salt has been purified by crystallization from 

 two parts ethyl acetate and one part 80 per 

 cent, ethyl alcohol, or by extraction with ether 

 and subsequent crystallization, with little or 

 no change in its composition. Furthermore, 

 the salt may be decomposed with ammonium 

 carbonate (Bergell) and the free lecithin again 

 converted into its cadmiimi chloride salt; this 

 salt will still have the same elementary com- 

 position. 



A more convincing proof of the chemical 

 individuality of lecithin is found in the prep- 

 aration of hydro-lecithin. Lecithin (especially 

 those samples which have been washed with 



a Levene, P. A., and West, C. J., J. Biol. Chem., 

 1918, 33, 111; 34 (in press). 



water and acetone, according to the directions 

 of MacLean) is very readily reduced with 

 hydrogen (using Paal's method, with colloidal 

 palladium as the catalyzer) and yields a crys- 

 talline tetrahydrolecithin, which may be ob- 

 tained in an analytically pure form by crys- 

 tallization from methyl ethyl ketone, and once 

 pure, may be recrystallized repeatedly, without 

 change in composition, from such solvents as 

 methyl ethyl ketone, alcohol, or ethyl acetate. 

 If, as Barbieri claims, fats are present, they 

 would remain in the methyl ethyl ketone 

 liquors; our experience in the purification of 

 cerebrosides indicates that this is one of the 

 best solvents for the removal of fat. 



We have also combined these two processes. 

 Lecithin has been precipitated from alcoholic 

 solution by cadmium chloride, the salt decom- 

 posed with ammonium carbonate, the free leci- 

 thin washed with water and acetone, and then 

 reduced with hydrogen. In this way Levene 

 and West have obtained a chemically pure 

 tetrahydrolecithin. 



It is hard to believe that a mixture of 

 choline, glycerides, and phosphates, such as 

 Barbieri claims for lecithin, can be subjected 

 to the above methods of treatment and give, 

 in every instance, a body with identical chem- 

 ical composition. Rather, I believe, it is 

 easier to accept the chemical individuality of 

 lecithin. 



Clarence J. West 



Washington, D. C. 



desmognathus fuscus [sic] 

 Full many a biologist, in his use of the 

 classics, has encountered two special stumb- 

 ling-blocks; the fourth Latin declension, and 

 the Greek noun whose gender does not fit its 

 form. 



Concerning the first of these, so many anat- 

 omical nouns, among them certain of the most 

 commonly used ones, belong to this weak form 

 of declension that the student of anatomy may 

 almost consider the fourth the commonest one 

 for masculines in -us. He meets with ductus, 

 arcus, fetus, plexus, and nexus; with pro- 

 cessus, recessus, meatus, tractus, and sinus, 

 while the five senses, with sensus itself, are 



